1. Field of the Invention
The present invention relates to a differential circuit, in particular, the invention relates to a differential circuit with suppressed output offset.
2. Related Prior Art
A Japanese Patent Application published as JP-2001-320249A has disclosed a circuit that includes a trans-impedance amplifier (hereafter denoted as TIA) and a differential amplifier. The TIA converts a photocurrent into a voltage signal. The differential amplifier amplifies this voltage signal and converts the single phase signal to two signals complementary to each other. The output of the TIA is filtered and led to one of inputs of the differential amplifier.
When the transistors implemented within the differential amplifier show lesser breakdown characteristic, namely, the collector current of the transistor increases at high collector biases even when the base bias current is kept low, the complementary signals output from the differential amplifier vary an offset voltage thereof depending on the input current.